Binocular eyepiece

Abstract

A wide-field binocular eyepiece preferably for use with a flat image display system. The eyepiece includes a biconvex thick lens having concentric spherical lens surfaces whose radii are selected to satisfy the aplanatic condition. To minimize chromatic aberration, the biconvex thick lens may be formed of a plurality of cemented elements having indices which are close to each other but having respective different dispersions.

What is claimed is: 
     
       1. A wide-field eyepiece for viewing an object surface plane, comprising a biconvex thick lens made of a material having an index n 1 , having first and second concentric spherical lens surfaces, each having a respective radius, a line through the common center of said lens surfaces, forming an optical axis of the system, said lens being arranged such that the second lens surface faces the object plane, and has a radius equal to the quotient of the radius of the first lens surface and the index n 1 , and means for forming a magnified virtual image of the object on a spherical surface which is concentric with said lens surfaces and has a radius equal to the product of the radius of the first lens surface and the index n 1 , said virtual image and the image formed on the second lens surface satisfying the aplanatic condition.   
     
     
       2. A wide-field eyepiece for viewing an object surface, comprising a biconvex thick lens comprising a plurality of cemented lens elements, each element having an index close to n 1 , said elements having respective different dispersions to provide correction for chromatic aberration, having first and second concentric spherical lens surfaces, each having a respective radius, a line through the common center of said lens surfaces forming an optical axis of the system, said lens being arranged such that the second lens surface faces the object plane, and has a radius equal to the quotient of the radius of the first lens surface and the index n 1 , and means for forming a magnified virtual image of the object on a spherical surface which is concentric with said lens surfaces and has a radius equal to the product of the radius of the first lens surface and the index n 1 , said virtual image and the image formed on the second lens surface satisfying the aplanatic condition.   
     
     
       3. A eyepiece as claimed in claim 1 or 2, characterized by comprising an additional element of the order 2, said thick lens constituting an element of the order 1,   said additional element being a convergent meniscus lens formed by p-2 addtional lens elements of the order 2, 3, . . . p, wherein p is a positive number greater than 2, each additional lens element being a convergence meniscus lens element made of a material having a respective index n 2 , n 3 , . . . n p  ; the concave surface of a respective menisucus lens element of the order i being a spherical lens surface having the center of curvature at the intersection of the optical axis with the virtual image formed by the element of the order i-1, wherein i has an arbitrary value greater than 1 and no greater than p; and the convex surface of each said additional lens element being a spherical surface concentric with the lens surfaces of said thick lens, and having a radius equal to the product of the radius of said first lens surface and the respective index n 1 , n 2 , . . . n i , the magnified virtual image formed by said meniscus lens of the order i lying on a spherical surface which is concentric with the respective convex surface and has a radius equal to the product of the radius of the respective convex surface and the index n i , thereby satisfying the aplanatic condition.   
     
     
       4. An eyepiece as claimed in claim 3, forming a periscopic system, comprising means for providing deflection inside said thick lens. 
     
     
       5. An eyepiece as claimed in claim 3, characterized in that each additional lens element comprises two cemented lens elements having respective indices which are close to each other, and having different dispersions selected to correct chromatic aberration. 
     
     
       6. An eyepiece as claimed in claim 5, characterized in that said thick lens and said additional lens elements are arranged close to each other to form a compact eyepiece. 
     
     
       7. An eyepiece as claimed in claim 6, forming a periscopic system, comprising means for providing deflection inside said thick lens.